1. Field
The invention relates to systems and methods for detecting facial expressions of vehicle drivers. More particularly, the invention relates to systems and methods for detecting drowsy facial expressions of vehicle drivers under changing illumination conditions.
2. Background
During operation of a vehicle, many drivers experience drowsiness which causes their eyes to shut for brief and sometimes even prolonged periods of time. Hence, being able to detect the drowsiness of an operator of a vehicle is becoming more and more important from a safety point of view.
In the past, a number of physiological sensors, such as respiratory, pulse, blood pressure, and driver movement sensors, have been used to detect drowsiness of drivers. These physiological sensors, however, have several drawbacks. For example, the reliability of these sensors is generally low and the attachment of these sensors is time-consuming and generally beyond the skill and interest of the driver. To alleviate these drawbacks, noninvasive sensors that do not require any set-up procedures to be performed by the driver have been developed.
Noninvasive video monitoring systems and methods monitor the face of an operator of a vehicle, such as a driver of a truck, to determine whether the operator may be falling asleep while operating the vehicle. As an example, digital imaging systems have been developed to continuously monitor a vertical eye width and determine a drowsiness factor based on the vertical eye width. These digital imaging systems require precise positioning of the eye to obtain 10 points of interest within the palpebral fissure (i.e., separation between the lower and upper eye lids). Under normal driving conditions, obtaining the precise positioning of the eye may not be feasible. Furthermore, variations in light intensity, eyeglass reflections, and normal driving facial movements make determination of the points of interest within the palpebral fissure likely to be unreliable.
Therefore, a need exists in the art for systems and methods for detecting drowsy facial expressions of vehicle drivers under changing illumination conditions.